# Rolling 12 Months Calculation

In this lesson you will learn how to write more complex DAX expressions through an example of calculating average rolling 12 months sales. for this example we will be using Calculate and some other functions to calculate sum or rolling 12 month, and number of months, and then dividing them. You will learn functions such as; CountRows, Divide, LastDate, NextDay, DatesBetween, and Calculate in this lesson.